System and method for remote sensing and/or analyzing spectral properties of targets and/or chemical speicies for detection and identification thereof

ABSTRACT

A method and a low-cost, robust and simple system for remote sensing and analyzing spectral properties of targets as a means to detect and identify them is introduced. The system can be highly portable but is usable in fixed locations or combination thereof. An aspect of the method and system includes the capability to distribute, modulate, aperture and spectrally analyze radiation emitted or absorbed by a volumetric target chemical species (solid, liquid or gas) or a target surface. Radiation is first collected by a single light gathering device, such as a lens, telescope, or mirror, and then distributed to multiple detectors through spectrally discriminating components and if desired through apertures to achieve this desired detection and identification.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention claims priority under 35 U.S.C. Section 119(e) ofthe earlier filing date of U.S. Provisional Application Ser. No.60/446,301, filed Feb. 10, 2003, entitled “Method and System forRadiation Modulation and Distribution to Multiple Detectors,” which ishereby incorporated by reference herein in its entirety.

The present application is also related to International Application No.PCT/US00/04027, filed Feb. 18, 2000, entitled “Passive Remote Sensor ofChemicals,” and corresponding U.S. application Ser. No. 09/936,833,filed Sep. 17, 2001, of which are assigned to the present assignee andare hereby incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to a method and system forremote sensing and/or analyzing spectral properties of targets and/orchemical species as a means to detect and identify them.

BACKGROUND OF THE INVENTION

Over the past several years, optical sensors have proven to have broadapplicability in the remote measurement of physical, chemical, andbiological phenomena. Such sensors can be used to measure a wide rangeof variables including but not limited to temperature, pressure, force,flow, radiation, liquid level, pH, displacement, humidity, vibration,strain, rotation, velocity, magnetic and electric fields, acceleration,acoustic fields, and to detect the presence of and identify one or morechemical species. In addition to this wide range of potential uses,optical sensors have a number of other benefits. For example, they areoften small, compact, light and have a longer lifetime than other typesof sensors. Optical sensors also tend to be immune to electromagneticinterference, can be electrically isolated, and often have highsensitivity. As a result, these sensors are not only replacingconventional sensors in many areas in science, engineering, and medicinebut researchers are beginning to create new kinds of sensors that haveunique properties. Since remote sensors do not require direct contactwith the measured target nor do they require sampling of any chemical,they provide the ability to scan large areas and volumes in a shortperiod of time.

There is utility and demand for optical sensors in an array ofindustries. Environmental and atmospheric monitoring, earth and spacesciences applications, industrial chemical processing and biotechnology,law enforcement, digital imaging, scanning, and printing are a fewexamples. In addition to these more established uses, there is an everincreasing need for devices and methods capable of early, passive, andremote detection of dangerous gases and other substances, particularlyfor security applications, but also for safety. Recently, the need forthese systems has been heightened by the spread of chemical warfaretechnology around the world and the increasing number of acts of globalterrorism, for example, threats against chemical plants can adverselyimpact large population centers in the vicinity of such plants. Indeed,the potential release of dangerous substances is now a serious concernnot only for the military, but domestically as well. The ability ofremote sensors to probe large volumes quickly and without actuallyentering a chemical cloud provides obvious benefits to first responderand law enforcement agencies.

The development of passive remote detectors has also been driven byother factors, such as the growing concern regarding the effects ofindustrial and vehicular emissions as well as other forms ofenvironmental pollution like pesticide over application. Remotedetectors are also needed to monitor and study long-term trends as wellas to identify and provide warnings regarding day-to-day environmentalproblems that may affect the health of local and global populations.

Although many remote sensors, e.g., lidar based systems and Fouriertransform interferometers, can meet most of these detection objectives,they are complex, expensive, large and heavy. There is a strong andunmet need for low-cost, highly portable and robust devices. Forexample, in many domestic security applications it is desired that eachpolice car or fire truck include a sensitive remote sensor of chemicalsthat can be hand carried by its crew to the site of potential incidentsand operated without actually endangering its operator. Similarly,public buildings require advanced warning to protect occupants againstchemical threats released indoors or outdoors. The cost of such a sensormust meet the needs of local government authorities and the level ofcomplexity and training must meet the ability of police officers orfirefighters.

In some optical remote sensing devices, designed to provide low-cost,robust and simple systems (e.g., differential absorptionradiometer—DAR), a method of collecting, modulating, and distributing(i.e., multiplexing) light to multiple detectors is required. Here lightis used to describe all types of electromagnetic radiation, includingbut not limited to x-rays, ultraviolet, visible, infrared and microwaveradiation. In such applications, multiple detectors are often fittedwith different filters (e.g., bandpass, notch, long pass, short pass,diffractive, or polarizers), for spectral analysis of a target. Further,many types of detectors must receive an amplitude modulated signal tooptimize their response (e.g., pyroelectric detectors) or to reducenoise and enhance detectivity by allowing for detection by demodulationin the frequency domain. While multiplexing,. i.e. providing acoincident field of view (FOV) for multiple detectors, may be achievedwith the use of multiple lenses, split lenses, or various configurationsof polarizers or split mirror, each of these techniques requires precisealignment of the optical components for each detector thereby increasingcomplexity and cost and making the system susceptible to misalignment byvibration, mild shocks, temperature variations, acoustics etc. therebyrendering them inadequate for their intended applications. Further,these techniques do not provide modulation of the collected radiationand reduce the available radiation by 1/N where N is the number ofdetectors. Radiation modulation is typically achieved by either spinningwheel or tuning fork choppers, or polarization modulators which mustthen be added to the already complex multiplexed system. Both modulationtechniques block radiation for a certain fraction of the modulationcycle, thereby reducing the collection and light management efficiency.Typical mechanical modulators use a 50% duty cycle (closed 50% of thetime).

Thus, there is a need in the art for a simple, robust and low-costmethod and system for simultaneous multiplexing and modulation that mayinclude placing multiple detectors behind a large single lens,distributing, modulating, aperturing, and spectrally analyzing thecollected optical signal among the detectors by sequentiallyilluminating the detectors through a masking system and spectrallyresolving components such as bandpass, notch, long pass, short pass,diffractive, or polarizers. In this case, detectors are illuminated atfull collection intensity, but for a fraction of the duty cycle,allowing the signal to be recorded only when an individual detector isilluminated by radiation from the target while avoiding noise from beingrecorded when that detector is not illuminated. Also, by densely packingthe detectors in linear, circular, or ring type arrays (thus reducingspace between adjacent detectors), sequential illumination can reduceradiation loss only to periods when radiation falls within the smallspaces between the adjacent detectors.

SUMMARY OF THE INVENTION

The present invention generally relates to a method and a low-cost,robust and simple system for remote sensing and analyzing spectralproperties of targets as a means to detect and identify them. The systemmay be portable, including man portable (such as, but not limitedthereto, a hand held device or personnel mounted) or it may be fixedlocation mounted or vehicle mounted. An aspect of an embodiment of thepresent invention includes a method and system to distribute, modulate,aperture and spectrally analyze radiation emitted or absorbed by avolumetric target chemical species (solid, liquid or gas) or a targetsurface. Radiation is first collected by a single light gatheringdevice, such as a lens, telescope, or mirror, and then distributed tomultiple detectors to achieve this desired detection and identification.This type of light distribution and modulation is useful, for example,in applications where multiple detectors are required to observe thesame scene while at the same time having the incident signal modulatedin time.

It should be appreciated that light, as mentioned through out thisdocument, should be interpreted to include all types of electromagneticradiation, including but not limited to infrared radiation, far-infraredradiation, microwave radiation, x-ray radiation, ultraviolet radiation,visible radiation, or any radiation that can be focused.

In one such application, each detector is equipped with a spectralfilter, and by distributing the radiation between these detectors asdescribed in the disclosure of the present invention, multi-spectralcharacteristics of the target area can be measured. The time dependentmodulation allows frequency domain, gated or windowed detection and theuse of low-cost detectors that require transient input (e.g.,pyroelectric detectors). Multiple radiation detectors are arranged withsmall or no physical space between them either in a circular pattern(e.g., on a disk or the like), ring pattern (i.e., facing inward oroutward of the circle), or in a linear or curved array. Either aspinning or rotating mirror or lens, a mirror oscillating around apivot, or a linearly oscillating lens or detector array is used todistribute the incoming signal to these detectors. One section of thedetection area may be left empty. When operation of the system isstopped, the mirror or lens may be pointed (“parked”) towards the emptyarea to protect the system from excess exposure (e.g., when facing thesun, but not limited thereto).

Since each detector is exposed to radiation for only a fraction of thespinning or oscillating cycle time, the output of each detector ismodulated. Since the gap between the detectors of the array can be madesmall or non-existent, most of the radiation collected by the lightgathering device throughout the entire scanning cycle must fall on theactive area of the detector array. Thus, unlike chopper-based systems,where radiation would normally be blocked by the chopper blades, thissystem can achieve nearly complete use of the collected radiation. Asynchronous demodulation process is then utilized to detect the signalin the time domain and separate the desired signal (which is located inthe time domain during a known phase of the spinning or oscillatingcycle or in the frequency domain at the known spinning or oscillatingcycle frequency) from the composite signal.

An aspect of an embodiment of the present invention provides anintegrated radiation gathering, modulation and distribution system forthe remote, passive detection of chemical species or other desired orrequired targets or portions of targets and/or chemical species. In anaspect, the system can detect one or more chemical species or othertargets without an active source of radiation independent from thatproduced by the species or the other target themselves and reliablyseparate the radiation emitted by the target species from that emittedby the optical equipment used for measurement.

An aspect of an embodiment of the present invention includes a systemfor remote sensing and analyzing spectral properties of at least onetarget and/or chemical species. The system comprising: a) a lightgathering device that collects and focuses incoming radiation emittedand/or absorbed and/or scattered by the target and/or chemical speciesto be analyzed; b) a folding optical element for directing the collectedand focused radiation from the light gathering device to at least one ofa plurality of detectors; c) at least one spectrally discriminatingoptical element in front of at least some of the detectors forspectrally resolving the collected radiation; d) wherein, the detectors,in relative movement with the folding optical element, producing anoutput signal; and e) a driving device to produce the relative movement;f) a device or method to monitor phase and frequency of the relativemovement; and g) a demodulation device, synchronous with the drivingdevice, to demodulate the output signal produced by the detectors.

An aspect of an embodiment of the present invention includes a systemfor remote sensing and analyzing spectral properties of at least onetarget and/or chemical species. The system comprising: a) a lightgathering device that collects, focuses, and directs incoming radiationemitted and/or absorbed and/or scattered by the target and/or chemicalspecies to be analyzed to one of a plurality of detectors; b) at leastone spectrally discriminating optical element in front of at least someof the detectors for spectrally resolving the collected radiation; c)the detectors, in relative movement with the light gathering device,producing an output signal; d) a driving device to produce the relativemovement between the light gathering device and the detectors; e) adevice or method to monitor phase and frequency of the relativemovement; and f) a demodulation device, synchronous with the drivingdevice, to demodulate the output signal produced by the detectors.

An aspect of an embodiment of the present invention includes a methodfor remote sensing and analyzing spectral properties of at least onetarget and/or chemical species. The method comprising: a) collecting andfocusing incoming radiation emitted and/or absorbed and/or scattered bythe target and/or chemical species to be analyzed, the collecting andfocusing being conducted from a gathering location; b) directing thefocused radiation, the directing being conducted at a directinglocation; c) spectrally analyzing the collected radiation at a spectralanalysis location, the spectral analysis produces spectral signaturethat can be used to identify target; d) detecting the directed andspectrally analyzed radiation at a detecting location, wherein thedirecting location and the detecting location is in relative movementfrom one another, the detection producing an output signal; e)monitoring the phase and frequency of the relative movement; and f)demodulating the output signal.

An aspect of an embodiment of the present invention includes a methodfor remote sensing and analyzing spectral properties of at least onetarget and/or chemical species. The method comprising: a) collecting,focusing, and directing incoming radiation emitted and/or absorbedand/or scattered by the target and/or chemical species to be analyzed,wherein the collecting, focusing, and directing being conducted from agathering location; b) spectrally analyzing the collected radiation at aspectral analysis location, the spectral analysis produces spectralsignature that, can be used to identify target; c) detecting thedirected and spectrally analyzed radiation at a detecting location,wherein the gathering location and the detecting location is in relativemovement from one another, the detection producing an output signal; d)monitoring the phase and frequency of the relative movement; and e)demodulating the output signal.

Further, an aspect of the methods and systems may include a processorwherein said processor receives output signals from the detectors and/ordemodulation device to separate background effects and noise from outputsignal to provide a net output that represents the spectralcharacteristics of the target and/or chemical species and use thosecharacteristics to detect and/or identify the targets and/or chemicalspecies. The detected and/or identified targets and/or chemical speciesare provided for at least one of: reducing or eliminating danger inpublic, private or military facilities or spaces or outdoors due to thepresence of toxic chemicals, to allow control of chemical or medicalmanufacturing processes, or to allow control or monitoring of pollutionor other processes due to plant or factory emission or other equipment.The system can be at least partially disposed in a housing defined ashand held device (palm device, suitcase, pack, wrist attachment, etc.),portable device, fixed location mounted, vehicle mounted, or roboticmounted or personnel mounted (helmet, pack, belt, back pack, clothing,weapon mounted, etc.). It should be appreciated that signals providedfor communications interfacing between modules or there within may be avariety of communications paths or channels. Such implementationsinclude, but not limited thereto, hardware, semiconductors, integratedcircuits, wire or cable, fiber optics, phone line, a cellular phonelink, an RF link, an infrared link, BLUE TOOTH, and other communicationschannels.

These and other objects, along with advantages and features of theinvention disclosed herein, will be made more apparent from thedescription, drawings, and claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the presentinvention, as well as the invention itself, will be more fullyunderstood from the following description of potential embodiments, whenread together with the accompanying drawings in which:

FIG. 1 schematically illustrates an embodiment of the present inventionsystem for remote sensing and analyzing spectral properties of targets,wherein a light gathering device is in optical communication with afolding optical element, such as a reflecting mirror, tilted at a largereflection angle such that the incoming collected and focused radiationis directed to the detector array.

FIG. 2 schematically illustrates an embodiment of the present inventionsystem for remote sensing and analyzing spectral properties of targets,wherein a light gathering device is in optical communication with afolding optical element, such as a reflecting mirror, tilted at a smallreflection angle such that the incoming collected and focused radiationis directed to the detector array.

FIG. 3 schematically illustrates an embodiment of the present inventionsystem for remote sensing and analyzing spectral properties of targets,wherein a light gathering device is in optical communication with afolding optical element, such as a reflecting multifaceted mirror, suchthat the incoming collected and focused radiation is directed to thedetector array.

FIG. 4 schematically illustrates an embodiment of the present inventionsystem for remote sensing and analyzing spectral properties of targets,wherein a light gathering device collects, focuses, and directsradiation emitted by the species or target to be detected or analyzed toan array of detectors, wherein a folding optical element is notnecessarily included.

FIG. 5 schematically illustrates an embodiment of the present inventionsystem for remote sensing and analyzing spectral properties of targets,wherein a light gathering device collects, focuses, and directsradiation emitted by the species or target to be detected or analyzed toan array of detectors, wherein a folding optical element is notnecessarily included.

FIGS. 6 and 7 generally correspond with FIGS. 1 and 2, respectively, andschematically illustrate embodiments of the present invention system forremote sensing and analyzing spectral properties of targets with thenotable feature of oscillation around a pivot (rather than rotation orspinning) which thereby provides the relative movement between thedetector array and light gathering device or folding optical element.

FIGS. 8 and 9 generally correspond with FIGS. 4 and 5, respectively, andschematically illustrate embodiments of the present invention system forremote sensing and analyzing spectral properties of targets with thenotable feature of linear oscillation (rather than rotation or spinning)which thereby provides the relative movement between the detector arrayand light gathering device or folding optical element.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, FIG. 1 schematically illustrates an embodiment ofthe present invention system for remote sensing and/or analyzingspectral properties of targets as a means to detect and identify them.An embodiment of the system 10 includes a light gathering device 20,which collects and focuses incoming radiation 1 emitted directly by thetarget or radiation from an illuminating source partially absorbed bythe target and/or chemical species 11 to be analyzed. A folding opticalelement 30 directs this collected and focused radiation from the lightgathering device 20 to an array 4 of detectors 8. A spectrallydiscriminating optical element 9 is in front of or in the optical pathof at least some of the detectors 8 for spectrally resolving thecollected radiation. Some examples of spectrally discriminating opticalelements 9 include, but not limited thereto, bandpass filters, notchfilters, long and short pass filters, diffraction elements, polarizerfilters, or combination thereof, etc. The folding optical element 30 isa mirror, tilted at a large reflection angle (whereby large reflectionangle is defined as the tilt angle of the mirror required to project theaxial ray 2 of the incoming radiation 1 away from the on-axis focusingcone of the light gathering device 20 as in FIG. 1. Similarly, a smallreflection angle is defined as any tilt angle of the mirror which willresult in projecting the axial ray 2 of the incoming radiation 1, intoits own path as defined by the on-axis focusing cone of the lightgathering device 20 as shown in FIG. 2) or reflection angle(s) asrequired or desired to direct the radiation away from the collectioncone of the light gathering device 20 that reflects radiation towardsthe detectors, which are arranged on an array that is configured as aring with the sensitive detecting element facing inward towards theradiation cone. With this configuration, the detectors do not blockincoming radiation. These multiple detectors 8 can be arrayed with smallor no physical space between them either in a ring pattern, as shown, oras will be discussed later, in a circular pattern, curved pattern orlinear array. In addition to this embodiment and embodiments discussedthroughout this document, it should be appreciated that the number ofindividual detectors can be increased or decreased and may be comprisedof varying sizes and types. Thus, it is preferred that the radiationcollected by the light gathering device 20 must fall sequentially on atleast one of the detectors 8 throughout the scan, achieving nearlycomplete use of the incoming radiation 1. This increases the signal tonoise ratio and sensitivity. The aperture device 12 is optional whendesired or required and can be placed on either the target side (front)of the gathering device 20 or the detector side (behind) of thegathering device.

It should be appreciated that an embodiment could scan one detector(s)for, say 90% of the time or as desired or required, move the beam off itfor just long enough to get a reference reading, then put the beam backon it, thereby achieving nearly complete use of the incoming radiation.

It should be appreciated that any lens, mirror, aperture device, mask orfilter mentioned in this document, as well as detector arrays, may be avariety of shapes and sizes. The surfaces of the lenses, mirrors,filters, arrays may be planar or curved (concave or convex),symmetrical, or asymmetrical, as well as having multiple contours andfaces on its surface.

It should be appreciated that light, as mentioned through out thisdocument, should be interpreted to include all types of electromagneticradiation, including but not limited to infrared radiation, far-infraredradiation, microwave radiation, x-ray radiation, ultraviolet radiation,visible radiation, or any radiation that can be focused. In anembodiment, the radiation incident on the array of detectors 8 ismodulated because the detectors 8 and the optical element 30 are inrelative movement. This movement or rotation is produced by a drivingdevice 6 (or other desired mechanism or technique) that is incommunication with the folding optical element 30 as shown by therotation arrow referenced as R or alternatively the detector array 4 mayrotate (not shown) or both optical element and detector array may be inrelative motion (not shown). A monitoring device 25 or monitoring methodsuch as software or hardware or combination thereof is in communicationwith the system, or as the example shown in FIG. 1 with the drivingdevice, to monitor the phase and frequency of the optical element(and/or detector array). In FIG. 1, the driving device 6 is showndriving the optical element 30. It should be noted that the lightgathering device 20 and folding optical element 30 are arranged in sucha way that nearly all of the radiation 1 emitted by, or passed though(i.e., emitted, scattered, or partially absorbed by), the species ortarget 11 to be detected or analyzed, is focused on one detector 8 inthe detector array 4 at a time. Thus, the detector array 4 is located ata distance from the light gathering device 20 that coincides or nearlycoincides with the focal plane FP of the light gathering device 20 asreflected by the folding optical element 30. In summary, in oneapproach, multiple detectors are arranged in a ring pattern (or desiredpattern) and placed such that, when the mirror is rotated about itscenter axis, the focal point of the incoming radiation 1, and thus theimage of the target scene 11, moves successively to the detectors 8 onthe array 4. In this manner, incoming radiation from the target, isdistributed to one detector at a time until all detectors are exposed tothe image after a complete revolution of the optical element or mirror.

The driving device 6 selects which individual detector the incomingradiation is focused on. By using a digitally controlled motor (e.g., astepping motor) or a continuous motor with an analog or digital encoder,it is possible to control the amount of time the radiation is focused onany given detector 8 in the detector array 4 or the exposure sequencebetween the detectors (e.g., skip or repeat exposure to certaindetectors). A symmetrical, constant velocity configuration involvesilluminating each detector for the same amount of time. However, inother applications, for example, when the response of one of thedetectors is low (or when desired), the incoming radiation may befocused on that detector for a longer period than the other detectors.Alternatively, more than one section of the detector may be exposed at agiven time. Similarly, it may be possible to fully skip some detectors,or expose some detectors more than once during any cycle if necessary.In addition, one section or more of the detector array 4 may be leftempty. As such, the space left empty (e.g., without any active detector)defines a gap (or a plurality of gaps), and towards which light can bedirected when the sensor is not in operation. When operation of thesystem is stopped, the folding optical element may be pointed (“parked”)such that the focal point is coincident with the empty area to protectthe system when excess exposure is detected, predicted, or when desired.Each detector 8 can be fitted with different filters, such as spectralfilters, if desired (e.g., bandpass, notch, long or short pass,diffractive, or polarizers) for analysis of different (e.g.,multi-spectral) characteristics in a target material.

In response to the incident collected, focused, modulated, and directedradiation the detectors of the array 4 produce an output signal 5. Thissignal is demodulated by a demodulation device 7, synchronous with thedriving device 6 that is causing either the folding optical element 30or the detector array 4 to move with some known frequency. Asynchronization signal may be provided to the demodulation device 7 bythe monitor device 25, or other alternative means. This demodulationdevice 7 can accomplish the necessary demodulation by using up to twoanalog to digital (A/D) converters to monitor the “on” signal of twoadjacent sensors while another converter may be required (depending ongeometry) to monitor the “off” state of a non-illuminated sensor. TwoA/D converters may be necessary for monitoring the on state of twoadjacent sensors because, as the focal point location is changed, aportion of the focused radiation can fall on two adjacent sensors inoptical sensor arrays where the inter-sensor spacing is significantlyless than the radiation beam size. These multiple A/D channels may beimplemented with a single A/D converter with an input channelmultiplexer. Samples of the detector signals are taken while radiationis focused on them. The decision to monitor a detector can be based onthe output of a stepper motor controller or an encoder. Referencesamples, possibly acquired at a slower sample rate, are obtained from adetector, typically immediately preceding exposure to focused radiation.A microprocessor can then be used to compute the weighted average of thedifference between the target-illuminated and reference signals of eachdetector, providing a usable baseband signal output proportional to theintensity of radiation reaching each sensor. Finally a processor 26 orthe like is in communication with the system to process the signals, asdesired or required from the detectors.

The light gathering device 20 may be a lens (e.g., refractive, Fresnel,GRIN, holographic, etc. and the like) as displayed in the figures butcan also be a mirror or telescope. It may be necessary to aperture thelight gathering device to prevent off-axis and unwanted radiation fromentering the sensor. A number of different devices can be used toprovide such aperturing whereby, for example, wherein the aperturedevice comprises an array of parallel optically transmitting channels orsubstantially parallel optically transmitting channels. For example ahoneycomb consisting of a plate with multiple parallel opticallytransmitting channels can be placed immediately in front or behind thelens. By selecting the width and length of these channels, the field ofview through the honeycomb can be designed to match the field of view ofthe sensor thereby providing blockage of off-axis radiation with minimalloss of on-axis radiation.

Alternatively, a mask consisting of an opaque disk or other shapedmember having an aperture-like hole can be attached to the foldingoptical element 30. The mask can be aligned such that the radiation coneformed by the incoming radiation 1 behind the light gathering device 20passes uninterrupted through the aperture while off axis radiation isblocked. By attaching the mask to the folding optical element 30, it canmove with it, thereby providing in-phase aperturing and masking.

A number of different structures can act as the folding optical element30. For example, the folding optical element 30 can be a mirror tiltedat large reflection angle and located at the center of a ring array ofdetectors 8. This type of optical element is represented in FIG. 1. Thedriving device 6 can cause either the mirror or the detector array 4 tomove, providing the desired distribution and modulation. It should beappreciated that the mirrors mentioned throughout this document may beat a variety of reflection angles as desired or required to provideillumination to detectors located outside the collection cone of thelight gathering device 20.

Next, turning to FIG. 2, FIG. 2 schematically illustrates an embodimentof the present invention system for remote sensing and/or analyzingspectral properties of targets as a means to detect and identify them.The light gathering device 20 is in optical communication with thefolding optical element 30 (which receives incoming radiation 1) thatcomprises a reflecting mirror 31, tilted at a small reflection angle,that is rotated by the driving device 6 or other mechanism as desiredsuch that the incoming collected and focused radiation is directed toone of the detectors 8 in the circular detector array 4, which islocated behind the light gathering device 20. In this configuration, thedetector array 4 is smaller than the light gathering device 20, andtherefore blocks only a fraction of the incoming focused radiation.Spectrally discriminating optical elements 9 may be placed in front ofor in the optical path of at least some of the detectors 8 forspectrally resolving the collected radiation. Some examples ofspectrally discriminating optical elements 9 include, but not limitedthereto, bandpass filters, notch filters, long and short pass filters,diffraction filters, polarizer filters, etc. The mirror 31 is rotated bythe driving device 6 as shown by the rotation arrow referenced as R oralternatively the detector array 4 may be rotated (not shown) or bothmay be rotated (not shown). For example, the detectors would rotatearound the line of the axial ray near the focal point. A monitoringdevice 25 or monitoring method such as software or hardware orcombination thereof is in communication with the system 10 to monitorthe phase and frequency of the optical element (and/or detector array).Finally a processor 26 or the like is in communication with the systemto process the signals, as desired or required from the detectors. Theaperture device 12 is optional when desired or required and can beplaced on either the target side (front) of the light gathering device20 or the optical element side (behind) of the light gathering device,and can be either stationary or rotating with the mirror 31.

It should be appreciated that, although not shown, the detectors do nothave to be in front of the lens. Rather, the mirror could both cycle thebeam and, by angling, tilt it out of the line of the incoming radiationcone (off to the side of the lens).

Next, turning to FIG. 3, FIG. 3 schematically illustrates an embodimentof the present invention system for remote sensing and/or analyzingspectral properties of targets as a means to detect and identify them.The folding optical element 30 can be a multifaceted mirror 32 spun bythe driving device 6 or other mechanism as desired. The mirror may berotated as shown by the arrow referenced as R. The detectors 8 arelocated in a semicircular or curved array 4 positioned such that as thedriving device 6 spins the multifaceted mirror 32, the radiation focuseson each of the detectors 8 in sequence. Spectrally discriminatingoptical elements 9 are placed in front of or in the optical path of atleast some of the detectors 8 for spectrally resolving the collectedradiation. Some examples of spectrally discriminating optical elements 9include, but not limited thereto, bandpass filters, notch filters, longand short pass filters, diffraction filters, polarizer filters, etc. Inan approach, the spinning multifaceted mirror is used to focus radiationon the array of detectors arranged on a curved surface such that eachdetector is in or near the focal plane FP of the optical system. Thisconfiguration permits a rapid modulation rate with a relatively slowmirror spinning frequency. In addition, detectors can be placed outsidethe radiation path, thereby preventing blockage of the incomingradiation.

Next, turning to FIG. 4, FIG. 4 schematically illustrates an embodimentof the present invention system for remote sensing and/or analyzingspectral properties of targets as a means to detect and identify them.Unlike the embodiments discussed above in FIGS. 1-3, the folding opticalelement is not specifically included, although it should be appreciatedthat it may be added. The system 10 comprises a light gathering device21 that collects, focuses, and directs radiation 1 emitted by thespecies or target 11 to be detected or analyzed to an array 4 ofdetectors 8. The detectors 8 are located in a circular shaped array 4 orother shape as desired or required. By directing the gathered radiation1 directly to the individual detectors, the light gathering device 21 inFIG. 4 fulfills both the role of the light gathering device and foldingoptical element similarly illustrated in, for example, FIG. 1.Spectrally discriminating optical elements 9 are in front of or in theoptical path of at least some of the detectors 8 for spectrallyresolving the collected radiation. Some examples of spectrallydiscriminating optical elements 9 include, but not limited thereto,bandpass filters, notch filters, long and short pass filters,diffraction filters, polarizer filters, etc. The aperture device 12 isoptional when desired or required and can be placed on either the targetside (front) of the light gathering device 21 or behind the lightgathering device, and can be either stationary or rotating with thelight gathering device 21. Again, the detector array 4 is located at adistance from the light gathering device 21 that coincides orsubstantially coincides with the focal plane FP of the light gatheringdevice 21. In an approach, to be discussed in greater detail below, thecircular detector array 4 is placed in the focal plane of a lens with anoff-axis focus and the lens is spun around an axis perpendicular to thelens that coincides with the axis of the circular detector array. Anadvantage of this approach is that, but not limited thereto, thespinning lens may be flat (e.g., when using Fresnel or holographiclens), thereby reducing aerodynamic drag below the level of thearrangement using an angled, rotating mirror. Another advantage is thatthe number of optical elements can be reduced below their number in thearrangement using an angled, rotating mirror thereby reducing cost andcomplexity. Off axis focus can be achieved by various methods, includingusing a holographic lens with one or more off axis focii or using aFresnel lens with one or more off axis focii.

The radiation reaching the detector array 4 is modulated because thedetector array 4 is in relative movement with the light gathering device21. A driving device 6, with possibly the same characteristics describedabove, produces this relative movement. The driving device can causeeither the light gathering device 21 to rotate as shown by the arrow ofrotation referenced as R or alternatively the detector array 4 to rotate(not shown) or both (not shown). In FIG. 4, the driving device 6 isshown connected to the light gathering device 21.

Once exposed to radiation, the detectors 8 produce an output signal 5that is directed to a demodulation device 7 which may operate in thesame manner as described above. A number of different structures can beused as the light gathering device 21. In FIG. 4, the light gatheringdevice 21 is a lens with an off-axis focus 14 (shown in FIG. 4 with alinear focal offset, but may also be angularly offset, as long as the FPof the lens rotates as to place the collected radiation sequentially onthe detectors) spun around its own central axis by the driving device 6.The central rotational axis 15 of the lens 21 is aligned with thecentral axis 17 of the detector array 8, which is fixed, such that thesource radiation 1, as focused by the lens 21, is incident on one of theindividual detectors 8 at a time (or as per a desired or requiredsequence) having a lens focal axis referenced as 14. Alternatively, butnot shown, the light gathering device, lens 21 and the detector array 4can be arranged in the same way, but the lens 21 can be fixed and thedetector array 4 can be rotated about its central rotational axis 17 bythe driving device 6 or the like.

Next, turning to FIG. 5, FIG. 5 schematically illustrates an embodimentof the present invention system for remote sensing and/or analyzingspectral properties of targets as a means to detect and identify them.The light gathering device 20 is again a lens 22. In this embodiment,the lens has a central axis focus 14. Spectrally discriminating opticalelements 9 are placed in front of or in the optical path of at leastsome of the detectors 8 for spectrally resolving the collectedradiation. Some examples of spectrally discriminating optical elements 9include, but not limited thereto, bandpass filters, notch filters, longand short pass filters, diffraction filters, polarizer filters, etc.This lens 22 is spun, as shown by the arrow of rotation referenced as R,around an optically off-center axis 15 of the lens by the driving device6 coinciding with the central rotational axis 17 of the detector array 4to modulate and distribute the radiation to the individual detectors 8.Alternatively, but not shown, the lens 22 and the detector array 4 canbe arranged in a similar fashion, but the lens 22 can be fixed and thedetector array 4 can be rotated about its central rotational axis 17 bythe driving device 6 to produce the desired modulation (or both the lensand array can spin). The aperture device 12 is optional when desired orrequired and can be placed on either the target side (front) of thelight gathering device 22 or behind the light gathering device, and canbe either stationary or rotating with the light gathering device 22 orwith the detector array 4.

Next, referring to FIGS. 6-7, FIGS. 6 and 7 generally correspond withFIGS. 1 and 2, respectively, and schematically illustrate embodiments ofthe present invention system for remote sensing and/or analyzingspectral properties of targets as a means to detect and identify themwith the notable feature of angular oscillation around a pivot (asopposed to spinning or rotation) which thereby provides the relativemovement between the detector array and light gathering device orfolding optical element. Turning to FIG. 6, the folding optical device30 (e.g., mirror) or light gathering device 20 (e.g., lens) oscillatesangularly about a pivot point P or pivot axis (such a pivot axis is notnecessarily coincident with the optical axis of the folding opticaldevice) as indicated by arrow referenced as O. Alternatively, the lineardetector array 4 may oscillate laterally along a line connecting thecenters of the detectors, as shown by the dashed arrow referenced as OL.Moreover, it is conceivable that both the optical device 30 or lightgathering device 20 and linear detector array 4 may oscillate (notshown). Accordingly, it should be appreciated that aspects as discussedthroughout this document can be equally or substantially applied to FIG.6. The aperture device 12 is optional when desired or required and canbe placed on either the target side (front) of the light gatheringdevice 20 or behind the light gathering device, and can be eitherstationary or oscillate with the folding optical element 22 as necessaryfor the aperture to track the beam.

Turning to FIGS. 7(A)-(B) the folding optical device 30 (e.g., mirror)oscillates angularly about a pivot point P or pivot axis as indicated byarrow referenced as O. The mirror may be tilted at a small-reflectionangle as shown in FIGS. 7(A)-(B) or may be perpendicular to the opticalaxis of the light gathering device 20 when in its neutral position. Asschematically shown in FIG. 7(A), the pivot point P or pivot axis isaligned substantially parallel with the paper as illustrated.Alternatively, the linear detector array 4 may oscillate laterally alonga line connecting the centers of the detectors, as shown by the dashedarrow referenced as OL. Whereas, as schematically shown in FIG. 7(B),the pivot point P or pivot axis is aligned perpendicular to the paper asillustrated. Alternatively, the linear detector array 4 may oscillatelaterally along a line connecting the centers of the detectors, as shownby the dashed arrow referenced as OL. Moreover, it is conceivable thatboth the folding optical device 30,and linear detector array 4 mayoscillate (not shown). Accordingly, it should be appreciated thataspects as discussed throughout this document can be equally orsubstantially applied to FIG. 7. The aperture device 12 is optional whendesired or required and can be placed on either the target side (front)of the light gathering device 20 or behind the light gathering device,and can be either stationary or oscillate with the folding opticalelement 22.

Next, referring to FIGS. 8 and 9, FIGS. 8 and 9 generally correspondwith FIGS. 4 and 5, respectively, and schematically illustrateembodiments of the present invention system for remote sensing and/oranalyzing spectral properties of targets as a means to detect andidentify them with the notable feature of linear oscillation of thelight gathering device 20 along a line that is parallel to the lineconnecting the centers of the detectors 8 on the array 4 (as opposed tospinning or rotation) which thereby provides the relative movementbetween the detector array and light gathering device or folding opticalelement. The light gathering device 20 (e.g., lens) oscillates laterallyas indicated by arrow referenced as OL. Alternatively, the lineardetector array 4 may oscillate laterally along a line connecting thecenters of the detectors 8, as shown by the dashed arrow referenced asOL. Moreover, it is conceivable that both the optical device or lightgathering device and linear detector array may oscillate (not shown).Accordingly, it should be appreciated that aspects as discussed hereincan be equally applied to FIGS. 8 and 9. The aperture device 12 isoptional when desired or required and can be placed on either the targetside (front) of the light gathering device 20 or behind the lightgathering device, and can be either stationary or oscillating with thelight gathering device 20 or with the detector array 4.

Applicable for, but not required thereto, all of the distributionmethods and systems described herein, nearly 100% of the desiredincoming signal is delivered to the detectors 8 and, with aperturingeach detector 8 views nearly the same scene even when the sensor is inmotion as may be the case when operated while hand-carried by a person,or operated from a vehicle such as a car, helicopter, robot, unmannedair vehicle and the like.

In addition to distribution, modulation of the incoming radiation isachieved using the described method and system herein. In an embodiment,signal from a detector when the mirror, lens, or detector array isrotated to a position such that the focal point does not coincide with adetector provides a reference, or off-signal, while signal due toincoming radiation in the FOV, or the on-signal, is achieved when thefocal point is aligned with the detector. However, to ensure a stablereference signal, off-axis incoming radiation must be blocked, orapertured, to prevent back reflection to a detector in the referenceportion of the cycle of modulation or exposure to undesired componentsin the target areas. This blocking may be achieved with masks on thelens or the moving mirror (e.g., a mask may consist of an opaque diskwith a hole located such that rays that are part of the incomingradiation 1 are transmitted unobstructed whereas the undesired off-axisrays are blocked), or aperturing devices, such as a honeycomb structure,placed in front of or behind the lens. This non-reflecting mask orradiation blocking aperture is placed on or near either side of thelens, mirror, or near the detectors in a manner to prevent radiationfrom outside the sensor from being reflected to each detectorsuccessively for a sufficient portion of the cyclical period to acquirea stable reference (typically a small fraction of a single rotation oroscillation period). With this mask or aperture, the incoming radiation1 reaches a single detector as the desired signal and any otherradiation from outside the sensor is not incident on that detector forsome masked portion of the cycle; thus, a stable differentialmeasurement may be achieved.

Frequently, optical filters, which also may radiate (mostly in the farinfrared range of the spectrum) to the detectors, are mounted in frontof the detectors; similarly, other parts of the sensor may radiate tothe detectors; however, since the radiation emitted by the filters orcomponents of the sensor itself, is not modulated using this method, theundesired radiation signal from the filters or the sensor may beseparated from the desired incoming signal. The modulation frequency asexperienced by any of the detectors is identical to the mirror or lensspinning, mirror-facet passing, or mirror or lens oscillating frequencyif the motional element cycles at a constant rate. The modulationfrequency of each detector can also be controlled actively by employinga stepper motor, linear motor or encoded analog motor as the motiveelement. Thus, when the angular frequency of the mirror or the detectorsis actively controlled and varies, either during each cycle or fromcycle to cycle, the actual modulation frequency is known.

Alternatively, rather than a stepper motor, linear or encoder motor, bymonitoring the phase and frequency of the mirror, the time at which eachdetector is exposed to the target area is known and the signalassociated with that event can be recorded, whereas signal at othertimes can either be rejected or recorded separately as a reference. As aresult, a monitoring technique or method is achieved.

Once the radiation is distributed and modulated, the detector responseto the incoming radiation must be determined. Typically, analog lock-inamplifiers are optimized for accurate demodulation of signals with a 50%duty cycle modulation. The attainable signal duty cycle associated withthe described distribution and modulation method when using an equaldwell time per sensor is approximately 100%/n where n is the number ofdetectors. Thus, a demodulation method matched to this signal pattern ispreferred. Up to two analog to digital (A/D) converters are used tomonitor the (on) signal of two adjacent detectors while anotherconverter may be required (depending on geometry) to monitor the (off)reference state of a non-illuminated detector. Two A/D converters may benecessary for monitoring the (on) signal of two adjacent detectorsbecause, as the focal point location is changed, a portion of thefocused signal can fall on two adjacent detectors for detector arrayswhere the interdetector spacing is significantly less than the focusedbeam size. These multiple A/D channels may be implemented with a singleA/D converter with an input channel multiplexer. Samples of the detectorsignals are taken while radiation is focused on them. The decision tomonitor a detector can be based on the output of a stepper motorcontroller, linear motor controller or an encoder. Reference samples,possibly acquired at a slower sample rate, are obtained from a detectorpreceding exposure to focused radiation. A microprocessor can then beused to compute the difference of the weighted averages of the (on andoff) signals of each detector, providing an output proportional to theintensity of light reaching each detector from the target.

As can be applied to the various embodiments discussed throughout thisdocument, the processor 26 or the like receives output signals from thedetector array 4 and/or demodulation device 7 to detect and/or identifysaid targets and/or chemical species 11. Having detected the targetsthis spectral information can be utilized for a variety of applications,including but not limited thereto, the following: environmental andatmospheric monitoring, such as pollution control including but notlimited to factory emission, vehicle emission, etc., militaryapplications for detecting threat chemical gases, anti-terroristapplications for detecting of threat chemical gases, in industrialapplications to monitor and control chemical processes including but notlimited to quality control, process progress, safety, etc., in the oilindustry to monitor and control oil or gas leaks, in the pharmaceuticalindustry to monitor and control medicine production processes, buildingsecurity applications to monitor the buildup of various gases. Thesystem can be at least partially or entirely disposed in a module orhousing that is defined as either a: hand held device, portable device,fixed location mounted, vehicle mounted, robotic mounted and/orpersonnel mounted, or combination thereof.

The following patents, patent applications and publications are herebyincorporated by reference herein in their entirety:

U.S. Pat. No. 6,111,248 to Melendez et al, entitled “Self-ContainedOptical Sensor System;”

U.S. Pat. No. 5,930,027 to Mentzer et al., entitled “DigitallyControlled Fiber Optic Light Modulation System;”

U.S. Pat. No. 5,585,622 to Durst et al., entitled “Optical Sensor withMirror Toggling;”

U.S. Pat. No. 5,338,933 to Reeves et al., entitled “Scanning OpticalSensor;”

U.S. Pat. No. 4,980,547 to Griffin, entitled “Light Distribution andDetection Apparatus;”

U.S. Pat. No. 4,778,988 to Henderson, entitled “Displacement Detection;”

U.S. Pat. No. 4,669,817 to Mori, entitled “Apparatus for Time-SharingLight Distribution;”

International Publication WO 00/55602 to Laufer, entitled “PassiveRemote Sensor of Chemicals;”

U.S. Pat. No. 5,479,258 to Hinnrichs et al., entitled “ImageMultispectral Sensing;”

U.S. Pat. No. 5,128,797 to Sachse et al., entitled “Non-MechanicalOptical Path Switching and its Application to Dual Beam SpectroscopyIncluding Gas Filter Correlation Radiometry;”

U.S. Pat. No. 4,790,654 to Clarke, entitled “Spectral Filter;”

U.S. Pat. No. 3,955,891 to Knight et al., entitled “CorrelationSpectrometer;”

U.S. Pat. No. 6,057,923 to Sachse entitled “Optical Path Switching BasedDifferential Absorption Radiometry for Substance Detection;”

U.S. Pat. No. 5,210,702 to Bishop et al. entitled “Apparatus for RemoteAnalysis of Vehicle Emissions”

U.S. Pat. No. 5,319,199 to Stedman, entitled “Apparatus for RemoteAnalysis of Vehicle Emissions;”

U.S. Pat. No. 5,371,367 to DiDomenico et al. entitles “Remote SensorDevice for Monitoring Motor Vehicle Exhaust Systems”

U.S. Pat. No. 5,401,967 to Stedman entitled “Apparatus for RemoteAnalysis of Vehicle Emissions;”

U.S. Pat. No. 5,489,777 to Stedman entitled “Apparatus for RemoteAnalysis of Vehicle Emissions Using Reflective Thermography;”

U.S. Pat. No. 5,498,872 to Stedman entitled “Apparatus for RemoteAnalysis of Vehicle Emissions;”

U.S. Pat. No. 6,064,488 to Brand et al. entitled “Method and Apparatusfor in Situ Gas Concentration Measurement;”

U.S. Pat. No. 5,886,247 to Rabbett entitled “High Sensitivity GasDetection;”

G. Laufer, A. Ben-David, Optimized Differential Absorption Radiometer(DAR) for Remote Sensing of Chemical Effluents, App. Opt., 41,2263-2273, 2002; and

S. K. Holland, R. H. Krauss, G. Laufer, Demonstration and Evaluation ofan Uncooled LiTaO₃ Detector Based Differential Absorption Radiometer forRemote Sensing of Chemical Effluents, to be published, Opt. Eng., 2004.

In summary, the present invention provides a low-cost, robust and simplesystem and method for remote sensing and analyzing spectral propertiesof targets as a means to detect and identify them.

Still other embodiments will become readily apparent to those skilled inthis art from reading the above-recited detailed description anddrawings of certain exemplary embodiments. It should be understood thatnumerous variations, modifications, and additional embodiments arepossible, and accordingly, all such variations, modifications, andembodiments are to be regarded as being within the spirit and scope ofthe appended claims. For example, regardless of the content of anyportion (e.g., title, section, abstract, drawing figure, etc.) of thisapplication, unless clearly specified to the contrary, there is norequirement for any particular described or illustrated activity orelement, any particular sequence of such activities, any particularsize, speed, dimension or frequency, or any particular interrelationshipof such elements. Moreover, any activity can be repeated, any activitycan be performed by multiple entities, and/or any element can beduplicated. Further, any activity or element can be excluded, thesequence of activities can vary, and/or the interrelationship ofelements can vary. Accordingly, the descriptions and drawings are to beregarded as illustrative in nature, and not as restrictive.

1. A system for remote sensing and analyzing spectral properties of atleast one target and/or chemical species, said system comprising: alight gathering device that collects and focuses incoming radiationemitted and/or absorbed and/or scattered by the target and/or chemicalspecies to be analyzed; a folding optical element for directing saidcollected and focused radiation from said light gathering device to atleast one of a plurality of detectors; at least one spectrallydiscriminating optical element in front of at least some of saiddetectors for spectrally resolving said collected radiation; saiddetectors, in relative movement with said folding optical element,producing an output signal; and a driving device to produce saidrelative movement; a device or method to monitor phase and frequency ofthe relative movement; and a demodulation device, synchronous with saiddriving device, to demodulate said output signal produced by saiddetectors.
 2. The system of claim 1, wherein said light gathering devicecomprises a lens.
 3. The system of claim 1, wherein said detectorscomprise an array.
 4. The system of claim 3, wherein said arraycomprises at least one of a curved array, circular array, ring array, orlinear array.
 5. The system of claim 3, wherein said array is rotated oroscillated to provide said relative movement.
 6. The system of claim 1,wherein said array includes at least one gap, said at least one gapdefined as without any active detector and towards which light can bedirected when array is not operational.
 7. The system of claim 1,wherein said spectrally discriminating optical element comprises atleast one of bandpass filters, notch filters, long and short passfilters, diffraction filters or polarizer filters or combination of atleast one of a bandpass filter, notch filter, long pass filter, shortpass filter or polarizer filter.
 8. The system of claim 1, wherein saidfolding optical element comprises a multifaceted mirror.
 9. The systemof claim 1, wherein said folding optical element is tilted.
 10. Thesystem of claim 9, wherein the tilt is a large reflection angle, whereinlarge reflection angle provides ability to project the axial ray awayfrom incoming radiation that is focused by the light gathering device.11. The system of claim 10, wherein said mirror is rotated by saiddriving device to provide said relative movement.
 12. The system ofclaim 10, wherein said plurality of detectors is rotated around saidmirror by said driving device to provide said relative movement.
 13. Thesystem of claim 9, wherein the tilt is a small reflection angle, whereinsmall reflection angle provides ability to project the axial ray towardincoming radiation that is focused by the light gathering device. 14.The system of claim 13, wherein said mirror is rotated by said drivingdevice to provide said relative movement.
 15. The system of claim 13,wherein said plurality of detectors is rotated by said driving device toprovide said relative movement.
 16. The system of claim 13, wherein saidplurality of detectors is rotated around the line of the axial ray nearthe focal point by said driving device to provide said relativemovement.
 17. The system of claim 1, wherein said folding opticalelement is rotated or oscillated to provide said relative movement. 18.The system of claim 1, wherein said folding optical element comprises amirror tilted and is located between said plurality of detectors andsaid light gathering device.
 19. The system of claim 1, wherein saidmirror is angularly oscillated around a pivot relative to said detectorsby said driving device to provide said relative movement.
 20. The systemof claim 19, wherein said mirror is tilted.
 21. The system of claim 1,wherein said plurality of detectors is linearly oscillated relative tosaid mirror by said driving device to provide said relative movement.22. The system of claim 21, wherein said mirror is tilted.
 23. Thesystem of claim 22, wherein said mirror is tilted at a large reflectionangle.
 24. The system of claim 1, wherein said driving device comprisesat least one of a digitally or analog controlled motor.
 25. The systemof claim 1, further comprising an aperture device along the optical pathfrom the target to said detectors to prevent off-axis incoming radiationfrom impinging on the detectors.
 26. The system of claim 25, whereinsaid aperture device comprises an array of parallel opticallytransmitting channels or substantially parallel optically transmittingchannels in front of said light gathering device.
 27. The system ofclaim 26, wherein said array of parallel or substantially paralleloptically transmitting channels is honeycomb structure.
 28. The systemof claim 25, wherein said aperture device comprises an array of paralleloptically transmitting channels or substantially parallel opticallytransmitting channels behind said light gathering device.
 29. The systemof claim 28, wherein said array of parallel or substantially paralleloptically transparent channels is honeycomb structure.
 30. The system ofclaim 25, wherein said aperture device comprises a mask, whereby saidmask allows radiation from said target to pass through to the currentlyilluminated detector(s) in the cycle sequence, whereby off-axisradiation is blocked or at least substantially blocked from thecurrently illuminated detector(s) and detector(s) selected to bemonitored for generating their reference signal.
 31. The system of claim30, wherein said mask is defined as at least one opaque member with ahole or gap forming an aperture adapted to allow the radiation to passthere through.
 32. The system of claim 31, wherein said opaque member isa disk, planar member, or substantially planar member, or memberconforming to the general shape of the detector array surface, operatingin front of said surface.
 33. The system of claim 1, further comprisinga processor wherein said processor receives output signals from saiddetectors and/or demodulation device to separate background effects andnoise from output signal to provide a net output that represents thespectral characteristics of the target and use those characteristics todetect and/or identify said targets.
 34. The system of claim 33, whereinsaid detected and/or identified targets are provided for at least oneof: reducing or eliminating danger in public, private or militaryfacilities or spaces or outdoors due to the presence of toxic chemicals,to allow control of chemical or medical manufacturing processes, or toallow control or monitoring of pollution or other processes due to plantor factory emission or other equipment.
 35. The system of claim 33,wherein said system is at least partially disposed in a housing definedas hand held device, portable device, fixed location mounted, vehiclemounted, or robotic mounted or personnel mounted.
 36. A system forremote sensing and analyzing spectral properties of at least one targetand/or chemical species, said system comprising: a light gatheringdevice that collects, focuses, and directs incoming radiation emittedand/or absorbed and/or scattered by the target and/or chemical speciesto be analyzed to one of a plurality of detectors; at least onespectrally discriminating optical element in front of at least some ofsaid detectors for spectrally resolving said collected radiation; saiddetectors, in relative movement with said light gathering device,producing an output signal; a driving device to produce said relativemovement between said light gathering device and said detectors; adevice or method to monitor phase and frequency of the relativemovement; and a demodulation device, synchronous with said drivingdevice, to demodulate said output signal produced by said detectors. 37.The system of claim 36, wherein said detectors comprise an array. 38.The system of claim 37, wherein said array comprises at least one of acurved array, circular array, ring array, or linear array.
 39. Thesystem of claim 38, wherein said array includes at least one gap, saidat least one gap defined as without any active detector and towardswhich light can be directed when array is not operational.
 40. Thesystem of claim 36, wherein: said detectors comprise an array; and saidlight gathering device comprises a lens with an off-axis focus spinningaround its own geometrically central axis, which is aligned with thecentral axis of said detector array, such that said source radiationfocuses on said elements of said detector array, in a sequence.
 41. Thesystem of claim 40, said sequence is defined by the radiation focusingon one of said individual detectors at a time.
 42. The system of claim40, said sequence is defined by the radiation focusing on at least aplurality of said individual detectors one at a time or a plurality at atime.
 43. The system of claim 36, wherein:. said detectors comprise anarray; and said light gathering device comprises a lens spinning aroundan axis which is off the geometrical center and that coincides with thegeometrically central axis of said detector array such that saidradiation focuses on said elements of said detector array, in asequence.
 44. The system of claim 43, said sequence is defined by theradiation focusing on one of said individual detectors at a time. 45.The system of claim 43, said sequence is defined by the radiationfocusing on at least a plurality of said individual detectors one at atime or a plurality at a time.
 46. The system of claim 36, wherein: saiddetectors comprise an array; and said light gathering device comprises afixed lens with an off-axis focus and said detector array is rotatedaround the geometrically central axis of said lens by said drivingdevice such that said radiation focuses on said elements of saiddetector array, in a sequence.
 47. The system of claim 46, said sequenceis defined by the radiation focusing on one of said individual detectorsat a time.
 48. The system of claim 46, said sequence is defined by theradiation focusing on at least a plurality of said individual detectorsone at a time or a plurality at a time.
 49. The system of claim 36,wherein: said detectors comprise an array; and said light gatheringdevice comprises a fixed lens and said detector array is rotated aroundan axis offset from but parallel to the geometrically central axis ofsaid lens by said driving device such that said radiation focuses onsaid elements of said detector array, in a sequence.
 50. The system ofclaim 49, said sequence is defined by the radiation focusing on one ofsaid individual detectors at a time.
 51. The system of claim 49, saidsequence is defined by the radiation focusing on at least a plurality ofsaid individual detectors one at a time or a plurality at a time. 52.The system of any one of claims 40, 43, 46, or 49, wherein said arraycomprises a circular array.
 53. The system of claim 36, wherein: saiddetectors comprise an array; and said light gathering device comprises alens linearly oscillating relative to said detector array such that saidradiation focuses on said elements of said detector array, in asequence.
 54. The system of claim 53, said sequence is defined by theradiation focusing on one of said individual detectors at a time. 55.The system of claim 53, said sequence is defined by the radiationfocusing on at least a plurality of said individual detectors one at atime or a plurality at a time.
 56. The system of claim 36, wherein: saiddetectors comprise an array; and said light gathering device comprises alens and said detector array oscillates linearly relative to the saidlens such that said radiation focuses on said elements of said detectorarray, in a sequence.
 57. The system of claim 56, said sequence isdefined by the radiation focusing on one of said individual detectors ata time.
 58. The system of claim 56, said sequence is defined by theradiation focusing on at least a plurality of said individual detectorsone at a time or a plurality at a time.
 59. The system of any one ofclaims 53 or 56, wherein said array comprises a linear array or curvedarray.
 60. The system of claim 36, wherein said driving device comprisesat least one of a digital or analog controlled motor.
 61. The system ofclaim 36, further comprising an aperture device along the optical pathfrom the target to said detectors to prevent off-axis incoming radiationfrom impinging on the detectors.
 62. The system of claim 61, whereinsaid aperture device comprises an array of parallel opticallytransparent channels or substantially parallel optically transparentchannels in front of said light gathering device.
 63. The system ofclaim 62, wherein said array of optically transparent parallel orsubstantially parallel channels is honeycomb structure.
 64. The systemof claim 61, wherein said aperture device comprises an array of paralleloptically transparent channels or substantially parallel opticallytransparent channels behind said light gathering device.
 65. The systemof claim 64, wherein said array of parallel optically transparentchannels is honeycomb structure.
 66. The system of claim 61, whereinsaid aperture device comprises a mask, whereby said mask allowsradiation from said target to pass there through to currentlyilluminated detector(s) in the cycle sequence, whereby off-axisradiation is blocked or at least substantially blocked from thecurrently illuminated detector(s) and detector(s) selected to bemonitored for generating their reference signal.
 67. The system of claim66, wherein said mask is defined as at least one opaque member with ahole or gap forming an aperture adapted to allow the radiation to passthere through.
 68. The system of claim 67, wherein said opaque member isa disk, planar member, or substantially planar member, or memberconforming to the general shape of the detector array surface, operatingin front of said surface.
 69. The system of claim 36, wherein saidspectrally discriminating optical element comprises at least one ofbandpass filters, notch filters, long and short pass filters,diffraction filters or polarizer filters or combination of at least oneof a bandpass filter, notch filter, long pass filter, short pass filteror polarizer filter.
 70. The system of claim 36, further comprising aprocessor wherein said processor receives output signals from saiddetectors and/or demodulation device to separate background effects andnoise from output signal to provide a net output that represents thespectral characteristics of the target and use those characteristics todetect and/or identify said targets.
 71. The system of claim 70, whereinsaid detected and/or identified targets are provided for at least oneof: reducing or eliminating danger in public, private or militaryfacilities or spaces or outdoors due to the presence of toxic chemicals,to allow control of chemical or medical manufacturing processes, or toallow control or monitoring of pollution or other process due to plantor factory emission or other equipment.
 72. The system of claim 70,wherein said system is at least partially disposed in a housing definedas hand held device, portable device, fixed mounted location, vehiclemounted, robotic mounted or personnel mounted.
 73. A method for remotesensing and analyzing spectral properties of at least one target and/orchemical species, said method comprising: collecting and focusingincoming radiation emitted and/or absorbed and/or scattered by thetarget and/or chemical species to be analyzed, said collecting andfocusing being conducted from a gathering location; directing saidfocused radiation, said directing being conducted at a directinglocation; spectrally analyzing said collected radiation at a spectralanalysis location, said spectral analysis produces spectral signaturethat can be used to identify target; detecting said directed andspectrally analyzed radiation at a detecting location, wherein saiddirecting location and said detecting location is in relative movementfrom one another, said detection producing an output signal; monitoringthe phase and frequency of the relative movement; and demodulating saidoutput signal.
 74. The method of claim 73, wherein said collecting andfocusing are is accomplished using a lens.
 75. The method of claim 73,wherein said collected radiation is spectrally analyzed by a pluralityof at least one of bandpass filters, notch filters, long and short passfilters, diffraction filters or polarizer filters or combination of atleast one of a bandpass filter, notch filter, long pass filter, shortpass filter or polarizer filter.
 76. The method of claim 73, whereinsaid detecting is accomplished by a plurality of detectors.
 77. Themethod of claim 76, wherein said detectors comprise an array.
 78. Themethod of claim 77, wherein said array includes at least one gap, saidat least one gap defined as without any active detector and towardswhich light can be directed when array is not operational.
 79. Themethod of claim 73, wherein said directing is accomplished by a foldingoptical element.
 80. The method of claim 79, wherein said foldingoptical element is tilted.
 81. The method of claim 80, wherein the tiltis a large reflection angle, wherein the large reflection angle providesability to project the axial ray away from the incoming radiation thatis focused by the light gathering device.
 82. The method of claim 80,wherein the tilt is a small reflection angle, wherein the smallreflection angle provides ability to project the axial ray toward theincoming radiation that is focused by the light gathering device. 83.The method of claim 79, wherein said folding optical element comprises areflecting mirror or multifaceted mirror.
 84. The method of claim 79,wherein said folding optical element is rotated or oscillated.
 85. Themethod of claim 79, wherein: said detecting is accomplished by aplurality of detectors forming an array; and said detector array isrotated around said tilted mirror.
 86. The method of claim 79, wherein:said detecting is accomplished by a plurality of detectors forming anarray; and said detector array is linearly oscillated relative to saidtilted mirror.
 87. The method of claim 73, wherein said driving isaccomplished by a driving device.
 88. The method of claim 87, whereinsaid driving device comprises at least one of a digitally or analogcontrolled motor.
 89. The method of claim 73, wherein: said directing isaccomplished by a folding optical element; and said detecting isaccomplished by a plurality of detectors.
 90. The method of claim 89,further comprising aperturing the incoming radiation to prevent off-axisincoming radiation from impinging on the detectors.
 91. A method forremote sensing and analyzing spectral properties of at least one targetand/or chemical species, said method comprising: collecting, focusing,and directing incoming radiation emitted and/or absorbed and/orscattered by the target and/or chemical species to be analyzed, saidcollecting, focusing, and directing being conducted from a gatheringlocation; spectrally analyzing said collected radiation at a spectralanalysis location, said spectral analysis produces spectral signaturethat can be used to identify target; detecting said directed andspectrally analyzed radiation at a detecting location, wherein saidgathering location and said detecting location is in relative movementfrom one another, said detection producing an output signal; monitoringthe phase and frequency of the relative movement; and demodulating saidoutput signal.
 92. The method of claim 91, wherein said collecting,focusing, and directing are accomplished using a lens.
 93. The method ofclaim 92, wherein said collected radiation is spectrally analyzed by atleast one of bandpass filters, notch filters, long and short passfilters, diffraction filters, or polarizer filters or combination of atleast one of bandpass filter, notch filter, long pass filter, short passfilter, diffraction filters, or polarizer filter or combination of abandpass filter, notch filter, long pass filter, short pass filter andpolarizer filter.
 94. The method of claim 91, wherein said detecting isaccomplished by a plurality of detectors.
 95. The method of claim 94,wherein said detectors comprise an array.
 96. The method of claim 95,wherein said array comprises at least one of a curved array, circulararray, ring array, or linear array.
 97. The method of claim 95, whereinsaid array includes at least one gap, said at least one gap defined aswithout any active detector and towards which light can be directed whenarray is not operational.
 98. The method of claim 91, wherein: saidcollecting, focusing, and focusing are accomplished using a lens; andsaid detecting is accomplished by a plurality of detectors.
 99. Themethod of claim 98, wherein: said detectors comprise a detector array;and said lens with an off-axis focus spinning around its owngeometrically central axis, which is aligned with the central axis ofsaid detector array, such that said source radiation focuses on theelements of the detector array, in a sequence.
 100. The method of claim98, wherein: said detectors comprise a detector array; and said lensspinning around an axis that is off its geometrical center but thatcoincides with the geometrically central axis of said detector arraysuch that said radiation focuses on the elements of the detector array,in a sequence.
 101. The method of claim 98, wherein: said detectorscomprise an array; and said lens is fixed with an off-axis focus andsaid detector array is rotated around the geometrically central axis ofsaid lens by said driving device such that said radiation focuses on theelements of the detector array, in a sequence.
 102. The method of claim98, wherein: said detectors comprise an array; and said lens is fixedand said detector array is rotated around an axis offset from butparallel to the geometrically central axis of said lens by said drivingdevice such that said radiation focuses on the elements of the detectorarray, in a sequence.
 103. The method of claim 98, wherein: saiddetectors comprise an array; and said light gathering device comprises alens linearly oscillating relative to said detector array such that saidradiation focuses on the elements of the detector array, in a sequence.104. The method of claim 98, wherein: said detectors comprise an array;and said light gathering device comprises a lens and said detector arrayoscillates linearly relative to the said lens such that said radiationfocuses on the elements of the detector array, in a sequence.
 105. Themethod of claim 98, wherein said driving is accomplished by a drivingdevice.
 106. The method of claim 98, further comprising aperturing theincoming radiation to prevent off-axis incoming radiation from impingingon the detectors.